include/Pythia8/PartonLevel.h

0001 // PartonLevel.h is a part of the PYTHIA event generator.
0002 // Copyright (C) 2024 Torbjorn Sjostrand.
0003 // PYTHIA is licenced under the GNU GPL v2 or later, see COPYING for details.
0004 // Please respect the MCnet Guidelines, see GUIDELINES for details.
0005
0006 // This file contains the main class for parton-level event generation
0007 // PartonLevel: administrates showers, multiparton interactions and remnants.
0008
0009 #ifndef Pythia8_PartonLevel_H
0010 #define Pythia8_PartonLevel_H
0011
0012 #include "Pythia8/Basics.h"
0013 #include "Pythia8/BeamParticle.h"
0014 #include "Pythia8/BeamRemnants.h"
0015 #include "Pythia8/Event.h"
0016 #include "Pythia8/HardDiffraction.h"
0017 #include "Pythia8/Info.h"
0018 #include "Pythia8/JunctionSplitting.h"
0019 #include "Pythia8/MergingHooks.h"
0020 #include "Pythia8/MultipartonInteractions.h"
0021 #include "Pythia8/ParticleData.h"
0022 #include "Pythia8/PartonSystems.h"
0023 #include "Pythia8/PartonVertex.h"
0024 #include "Pythia8/PhysicsBase.h"
0025 #include "Pythia8/PythiaStdlib.h"
0026 #include "Pythia8/ResonanceDecays.h"
0027 #include "Pythia8/RHadrons.h"
0028 #include "Pythia8/Settings.h"
0029 #include "Pythia8/Settings.h"
0030 #include "Pythia8/SharedPointers.h"
0031 #include "Pythia8/SigmaTotal.h"
0032 #include "Pythia8/SpaceShower.h"
0033 #include "Pythia8/StandardModel.h"
0034 #include "Pythia8/StringLength.h"
0035 #include "Pythia8/TimeShower.h"
0036 #include "Pythia8/UserHooks.h"
0037
0038 namespace Pythia8 {
0039
0040 //==========================================================================
0041
0042 // The PartonLevel class contains the top-level routines to generate
0043 // the partonic activity of an event.
0044
0045 class PartonLevel : public PhysicsBase {
0046
0047 public:
0048
0049   // Constructor.
0050   PartonLevel() = default;
0051
0052   // Initialization of all classes at the parton level.
0053   bool init( TimeShowerPtr timesDecPtrIn, TimeShowerPtr timesPtrIn,
0054     SpaceShowerPtr spacePtrIn, RHadrons* rHadronsPtrIn,
0055     MergingHooksPtr mergingHooksPtr, PartonVertexPtr partonVertexPtrIn,
0056     StringIntPtr stringInteractionPtrIn,
0057     bool useAsTrial);
0058
0059   // Special setup to allow switching between beam PDFs for MPI handling.
0060   // Not needed when MPI for incoming pomeron, since same for all beams.
0061   void initSwitchID( const vector<int>& idAList) {
0062     multiMB.initSwitchID(  idAList);
0063     multiSDA.initSwitchID( idAList);}
0064
0065   // Switch to new beam particle identities; for similar hadrons only.
0066   void setBeamID(int iPDFA = 0) {multiMB.setBeamID(iPDFA);
0067     multiSDA.setBeamID(iPDFA);}
0068
0069   // Generate the next parton-level process.
0070   bool next( Event& process, Event& event);
0071
0072   // Perform showers in resonance decay chains. (For special cases.)
0073   void setupShowerSys( Event& process, Event& event);
0074   bool resonanceShowers( Event& process, Event& event, bool skipForR);
0075
0076   // Perform decays and showers of W and Z emitted in shower.
0077   bool wzDecayShowers( Event& event);
0078
0079   // Tell whether failure was due to vetoing.
0080   bool hasVetoed() const {return doVeto;}
0081   bool hasVetoedDiff() const {return doDiffVeto;}
0082   bool hasVetoedMerging() const {return doMergingVeto;}
0083
0084   // Accumulate, print and reset statistics.
0085   void accumulate() {if (isResolved && !isDiff) multiPtr->accumulate();}
0086   void statistics(bool reset = false) {
0087     if (doMPI) multiMB.statistics(reset);}
0088   void resetStatistics() { if (doMPI) multiMB.resetStatistics(); }
0089
0090   // Reset PartonLevel object for trial shower usage.
0091   void resetTrial();
0092   // Provide the pT scale of the last branching in the shower.
0093   double pTLastInShower() { return pTLastBranch; }
0094   // Provide the type of the last branching in the shower.
0095   int typeLastInShower() { return typeLastBranch; }
0096
0097   // Check of any trial emissions could have been enhanced.
0098   bool canEnhanceTrial() { return doEnhanceTrial; }
0099   // Get enhanced trial emission evolution variable.
0100   double getEnhancedTrialPT() {
0101     if (canEnhanceTrial()) return infoPtr->weightContainerPtr->
0102       weightsSimpleShower.getEnhancedTrialPT();
0103     return 0.;
0104   }
0105   // Get enhanced trial emission weight.
0106   double getEnhancedTrialWeight() {
0107     if (canEnhanceTrial()) return infoPtr->weightContainerPtr->
0108       weightsSimpleShower.getEnhancedTrialWeight();
0109     return 1.;
0110   }
0111
0112   // Spare copies of normal beam pointers.
0113   BeamParticle*  beamHadAPtr{};
0114   BeamParticle*  beamHadBPtr{};
0115
0116   // Pointers to timelike showers for resonance decays and the rest.
0117   TimeShowerPtr  timesDecPtr{};
0118   TimeShowerPtr  timesPtr{};
0119
0120   // Pointer to spacelike showers.
0121   SpaceShowerPtr spacePtr{};
0122
0123 protected:
0124
0125   virtual void onInitInfoPtr() override {
0126     registerSubObject(multiMB);
0127     registerSubObject(multiSDA);
0128     registerSubObject(multiSDB);
0129     registerSubObject(multiCD);
0130     registerSubObject(multiGmGm);
0131     registerSubObject(remnants);
0132     registerSubObject(resonanceDecays);
0133     registerSubObject(junctionSplitting);
0134     registerSubObject(hardDiffraction);
0135   }
0136
0137 private:
0138
0139   // Constants: could only be changed in the code itself.
0140   static const int NTRY;
0141
0142   // Initialization data, mainly read from Settings.
0143   bool   doNonDiff{}, doDiffraction{}, doMPI{}, doMPIMB{}, doMPISDA{},
0144          doMPISDB{}, doMPICD{}, doMPIinit{}, doISR{}, doFSRduringProcess{},
0145          doFSRafterProcess{}, doFSRinResonances{}, doInterleaveResDec{},
0146          doRemnants{}, doSecondHard{}, hasOneLeptonBeam{}, hasTwoLeptonBeams{},
0147          hasPointLeptons{}, canVetoPT{}, canVetoStep{}, canVetoMPIStep{},
0148          canVetoEarly{}, canSetScale{}, allowRH{}, earlyResDec{},
0149          vetoWeakJets{}, canReconResSys{}, doReconnect{}, doHardDiff{},
0150          forceResonanceCR{}, doNDgamma{}, doMPIgmgm{}, showUnresGamma{};
0151   int    pTmaxMatchMPI;
0152   double mMinDiff{}, mWidthDiff{}, pMaxDiff{}, vetoWeakDeltaR2{};
0153
0154   // Event generation strategy. Number of steps. Maximum pT scales.
0155   bool   doVeto{};
0156   int    nMPI{}, nISR{}, nFSRinProc{}, nFSRinRes{}, nISRhard{}, nFSRhard{},
0157          typeLatest{}, nVetoStep{}, typeVetoStep{}, nVetoMPIStep{}, iSysNow{},
0158          reconnectMode{}, hardDiffSide{}, sampleTypeDiff{};
0159   double pTsaveMPI{}, pTsaveISR{}, pTsaveFSR{}, pTvetoPT{};
0160
0161   // Current event properties.
0162   bool   isNonDiff{}, isDiffA{}, isDiffB{}, isDiffC{}, isDiff{},
0163          isSingleDiff{}, isDoubleDiff{}, isCentralDiff{},
0164          isResolved{}, isResolvedA{}, isResolvedB{}, isResolvedC{},
0165          isHardDiffA{}, isHardDiffB{}, isHardDiff{}, doDiffVeto{},
0166          hardDiffSet{}, isElastic{}, twoHard{};
0167   int    sizeProcess{}, sizeEvent{}, nHardDone{}, nHardDoneRHad{}, iDS{};
0168   double eCMsave;
0169   vector<bool> inRHadDecay;
0170   vector<int>  iPosBefShow;
0171
0172   // Variables for photon inside electron.
0173   bool   hasGammaA{}, hasGammaB{}, beamHasGamma{}, beamAisGamma{},
0174          beamBisGamma{}, beamAhasGamma{}, beamBhasGamma{}, beamAhasResGamma{},
0175          beamBhasResGamma{}, beamHasResGamma{}, isGammaHadronDir{},
0176          sampleQ2gamma{};
0177   int    gammaMode{}, gammaModeEvent{}, gammaOffset{};
0178   double eCMsaveGamma{};
0179
0180   // Pointer to assign space-time vertices during parton evolution.
0181   PartonVertexPtr partonVertexPtr{};
0182
0183   // The generator classes for multiparton interactions.
0184   MultipartonInteractions  multiMB;
0185   MultipartonInteractions  multiSDA;
0186   MultipartonInteractions  multiSDB;
0187   MultipartonInteractions  multiCD;
0188   MultipartonInteractions* multiPtr{};
0189   MultipartonInteractions  multiGmGm;
0190
0191   // The generator class to construct beam-remnant kinematics.
0192   BeamRemnants remnants;
0193
0194   // The RHadrons class is used to fragment off and decay R-hadrons.
0195   RHadrons*    rHadronsPtr{};
0196
0197   // ResonanceDecay object does sequential resonance decays.
0198   ResonanceDecays resonanceDecays;
0199
0200   // The Colour reconnection class used to do colour reconnection.
0201   ColRecPtr colourReconnectionPtr{};
0202
0203   // The Junction splitting class used to split junctions systems.
0204   JunctionSplitting junctionSplitting;
0205
0206   // The Diffraction class is for hard diffraction selection.
0207   HardDiffraction hardDiffraction;
0208
0209   // Resolved diffraction: find how many systems should have it.
0210   int decideResolvedDiff( Event& process);
0211
0212   // Set up an unresolved process, i.e. elastic or diffractive.
0213   bool setupUnresolvedSys( Event& process, Event& event);
0214
0215   // Set up the hard process, excluding subsequent resonance decays.
0216   void setupHardSys( Event& process, Event& event);
0217
0218   // Resolved diffraction: pick whether to have it and set up for it.
0219   void setupResolvedDiff( Event& process);
0220
0221   // Resolved diffraction: restore normal behaviour.
0222   void leaveResolvedDiff( int iHardLoop, Event& process, Event& event);
0223
0224   // Hard diffraction: set up the process record.
0225   void setupHardDiff( Event& process);
0226
0227   // Hard diffraction: leave the process record.
0228   void leaveHardDiff( Event& process, Event& event, bool physical = true);
0229
0230   // Photon beam inside lepton beam: set up the parton level generation.
0231   bool setupResolvedLeptonGamma( Event& process);
0232
0233   // Photon beam inside lepton beam: recover the whole event and
0234   // add scattered leptons.
0235   void leaveResolvedLeptonGamma( Event& process, Event& event,
0236     bool physical = true);
0237
0238   // Set the photon collision mode for the current event.
0239   void saveGammaModeEvent( int gammaModeA, int gammaModeB);
0240
0241   // Photon beam inside lepton beam: set up the parton level generation.
0242   void cleanEventFromGamma( Event& event);
0243
0244   // Pointer to MergingHooks object for user interaction with the merging.
0245   MergingHooksPtr mergingHooksPtr{};
0246   // Parameters to specify trial shower usage.
0247   bool doTrial{};
0248   bool doEnhanceTrial{};
0249   int nTrialEmissions{};
0250   // Parameters to store to veto trial showers.
0251   double pTLastBranch{};
0252   int typeLastBranch{};
0253   // Parameters to specify merging usage.
0254   bool canRemoveEvent{}, canRemoveEmission{}, doMergingVeto{};
0255
0256 };
0257
0258 //==========================================================================
0259
0260 } // end namespace Pythia8
0261
0262 #endif // Pythia8_PartonLevel_H